One year on Mars and still roving: What has Curiosity gleaned so far? (+video)
The rover Curiosity has been exploring Mars for a year now, almost halfway through its mission. It has already helped to prove that Mars did once have water and an environment hospitable to life. Here's what's next.
One year into a 23-month mission, NASA's Mars rover Curiosity has assured its place in the history of planetary exploration as the most ambitious and one of the most successful attempts to date to explore the surface of another planet.Skip to next paragraph
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Even before the rover and its package of 10 science instruments wrapped up their first year of measurements, Curiosity's data allowed the mission's science team to answer the broadest question it had designed the rover to answer: Did Mars ever have an environment hospitable to microbial life?
Its testing ground: Gale Crater and the layered foothills of Mt. Sharp, a wind-smoothed mountain whose summit rises 18,000 feet from the crater floor.
But Curiosity didn't have to scale the foothills of Mt. Sharp to find the answer. It lay in the rover's own backyard. Rock formations within several hundred yards of the rover's landing site provided the answer: a resounding "yes."
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The science team already had reason to suspect this might be the case, judging from the images and other data from orbiters NASA had sent in its initial quest to "follow the water" in the hunt for habitability. The images suggested that water flowed through – and perhaps pooled in – the crater billions of years ago.
Researchers picked Curiosity's landing site on the basis of what looked to be cemented deposits exposed on the surface. Landing on or near these rocks would give them an early look at potentially revealing rock formations, provide scientifically interesting targets even as instruments were still undergoing their on-Mars tests, and serve as a hedge in case the rover malfunctioned later in the mission.
After a remarkable "sky crane" landing system put Curiosity's six wheels on the surface, the rover provided spectacular confirmation of once-flowing water in the crater, as well as of standing water.
It came in the form of rock outcroppings, themselves conglomerations of naturally cemented pebbles, which represent the jackpot find so far, according to Darby Dyer, a planetary scientist at Mount Holyoke College in South Hadley, Mass.
"We know that Mars is largely a volcanic planet but that there's been a lot of reworking" of the original volcanic rock, says Dr. Dyer, a member of the team gathering and analyzing data from Curiosity's ChemCam, a laser-spectrometer combo mounted on the rover's six-foot-tall mast. Of particular interest are so-called sedimentary rocks, which form in the presence of water.
"This is the first mission where we've seen the whole spectrum of sedimentary rocks," she says. These rocks are common on Earth, but researchers have never had close-ups of these same rock types on Mars.
Having those in hand represent "the most exciting thing on the mission, by far," she says.
The rocks speak to a time in Mars' distant past when water flowed for prolonged periods through Gale Crater – certainly longer than weeks or months, according to a formal analysis of the outcroppings published in the journal Science on May 31.
Water at least three feet deep and flowing at a pace of more than 1.6 miles an hour would have been needed to keep the largest pebbles in the conglomerate rolling along, noted a team led by Rebecca Williams, a senior scientist with the Planetary Sciences Institute in Tucson, Ariz., in the paper. The researchers deduced the long duration of the flow from the rounded edges of the outcroppings themselves.
Other analyses indicate that the soil and water chemistry at the time would have been mild enough to allow microbial life to thrive – a low salt content and clay minerals that speak of water perhaps fresh enough to drink.
Yet evidence for liquid water, widely seen as crucial for organic life, was only one leg of a triangle of potential habitability Curiosity revealed, notes John Grotzinger, a planetary scientist at the California Institute of Technology in Pasadena and the mission's lead scientist.